In general, a pulsator type washing machine performs washing under the control of a microcomputer for removing dirt from clothes, and beddings by using a softening action of detergent, friction of water circulation following rotation of a pulsator, and impact of the pulsator to laundry, after kind and amount of laundry is detected with a sensor, to set a washing method automatically accordingly, and washing water is supplied to a proper level according to the kind and amount of the laundry.
On the other hand, the drum type washing machine, washing laundry by using friction between laundry and drum rotated by driving force of a motor in a state the detergent, washing water, and the laundry are introduced into the drum, gives almost no damage to the laundry, causes no entangling of the laundry, and provides a washing effect of pounding and rubbing the laundry.
A related art drum type washing machine will be described briefly with reference to FIG. 1.
FIG. 1 illustrates a longitudinal section of a related art drum type washing machine, provided with a tub 2 in a cabinet 1, and a drum 3 rotatably mounted at a central portion of the tub 2.
Under the tub 2, there is a motor 5a having a motor pulley 18 coupled thereto through a shaft, and, in a rear of the drum 3, there is a drum shaft mounted thereon having a drum pulley 19 coupled thereto.
According to this, as the drum pulley 19 on the drum shaft and the motor pulley 18 coupled to the motor 5a are connected through a belt 20, a power transmission element, for transmission of driving force from the motor to the drum 3 through the belt 20.
Mounted on a front of the cabinet 1, there is a door 21, with a gasket 2 mounted between the door 21 and a tub 2.
In the meantime, between an underside of an upper portion of the cabinet 1 and an upper side of an outside circumference of the tub 2, there are hanging springs 23 for suspending the tub, and between a bottom of the cabinet 1 and a lower side of the outside circumference of the tub 2, there are dampers 24 for attenuating vibration of the tub 2 taking place at the time of spinning.
However, the related art washing machine has the following drawback since the related are washing machine has a structure in which the driving force is transmitted from the motor 5a to the drum 3 through the motor pulley 18, the drum pulley 19, and the belt 20 connecting the motor pulley 18 and the drum pulley 19.
First of all, because the driving force is transmitted to the drum 3, not directly, but through the belt 20 wound on the motor pulley 18 and the drum pulley 19, an energy loss takes place in a course of driving force transmission.
Moreover, because the driving force is transmitted to the drum 3, not directly, but through many components, such as the motor pulley 18, the drum pulley 19, the belt 20, and so on, much noise is generated in the power transmission.
The many components, such as the motor pulley 18, the drum pulley 19, the belt 20, and so on, required for transmission of the driving force of the motor Sa to the drum 3 cause to increase an assembly man-hours of the product.
Moreover, the many components required for transmission of the driving force of the motor 5a to the drum 3 increase a number and frequency of faults.
In short, the indirect transmission of the driving force from the motor 5a to the drum 3 by using the motor pulley, the drum pulley, and the belt is liable to cause trouble and noise, has many energy waste factors, and impairs washing capability.
Along with this, the tub 2 of stainless steel of the related art drum type washing machine costs high, has a poor processability, and is heavy.
In the meantime, instead of the indirect transmission of the driving force from the motor to the drum by using the belt and pulleys, though a direct drive drum type washing machine system has been introduced, the system has a drawback in that a stator directly secured to a rear wall of the tub fails to maintain concentricity of the stator due to damage or deformation of a fastening portion caused by vibration of the motor.
Moreover, in order to solve above problem, in a case a bearing housing is fabricated separate from the tub, not only assembly is difficult, but also the assembly occupies a large space as an entire bearing housing projects from the tub. In a case the bearing housing is fastened with screws or bolts, since the bearing housing is supported, not entirely, but only partially at one side thereof, the fastening is susceptible to vibration. Moreover, since a complicate water protection structure is required not only for the bearing itself, but also between the tub and the bearing, the structure has drawback in fabrication.
Together with this, the bearing housing is required to have an inner collar and an outer collar which are separate components for supporting the bearing mounted therein, and fabrication of the rotor is very difficult because of individual permanent magnets, steel plate, and a back yoke at a back side of the steel plate.
In the meantime, in order to solve the problem, a structure of the driving unit is introduced, in which the motor has a steel plate rotor having a back yoke provided separately, and the bearing housing not projected to an outside of the tub.
However, since the structure has a rotor with an axial projection from a rear wall of the rotor, and thread on an inside circumferential surface of the projection, for fastening a connector to the thread in the projection with a screw, the structure has a complicate rotor fabrication process and a poor processability, requiring to form the projection and the thread on the inside circumferential surface of the projection at the time of processing the rotor, and remove burrs therefrom.